"The “smart drug” culture has generally been thinking pharmaceutically rather than biologically...Any chemical support for intelligence should take into account the mind-damaging stresses that our culture can impose, and provide defense against those. In darkness and isolation, for example, the stress hormones increase, and the brain-protective steroids decrease. The memory improvement that results from taking pregnenolone or thyroid (which is needed for synthesizing pregnenolone from cholesterol) is the result of turning off the dulling and brain-dissolving stress hormones, allowing normal responsiveness to be restored." -Ray Peat, Intelligence & Metabolism